In January, Amazon announced that its Alexa virtual assistant would be built in to some new PCs from manufacturers including HP, Acer, and Asus. While Amazon hasn't announced anything specifically, that news puts it within the realm of possibility that Amazon could release Alexa as a standalone Windows app, too. Besides, playing music is already a tremendously popular feature of the Alexa agent; having a full Amazon Music app too just makes sense.

On the one hand, the move to launch Amazon Music on Windows 10 seems counterintuitive. The PC market is shrinking, while Amazon's own hardware businesses - like the Alexa-powered Echo speakers and its Kindle Fire tablets - are booming, according to all available indicators.

And yet, Windows 10 is still a massive market. Microsoft says in a blog post that there are now over 600 million Windows 10 PCs out there. That gives Amazon a big market to address, which could help it gain ground on Spotify and Apple Music, the first- and second-place most popular streaming services, respectively. Notably, Spotify is already available on the Windows Store, with a delayed Apple iTunes app coming soon.

Plus, Microsoft is still a major player in the demographic that every media company wants: Young people. While Google's low-cost Chromebooks dominate the educational market in the United States, Windows is overall the most popular operating system in classrooms around the world.

In the bigger picture, too, Microsoft is reportedly pushing "S Mode" - a Windows 10 feature that grants improvements to battery life and performance, with the tradeoff that you can only install software from the Windows Store. If Microsoft's ambitions are fulfilled and "S Mode" comes to many more PCs, it'll behoove Amazon, Apple, and Spotify to all have apps on the Windows Store, or else risk losing access to those users.

As for Microsoft itself, it doesn't really have a horse in this race. The company shuttered its own Groove Music streaming service in 2017, offering users a way to migrate their playlists to Spotify. And Microsoft and Amazon had previously announced an integration between Alexa and the Microsoft Cortana smart agent, too.